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Remote endarterectomy is a procedure by which a single incision is made at one position along a blood vessel to provide access to the blood vessel by some type of ring stripper. The remote endarterectomy procedure is often accomplished when the blood vessel is totally occluded. The ring stripper, which typically consists of a ring at the end of a long thin handle, is typically passed between the tunica intima (also called the intimal layer) and the tunica media under fluoroscopic guidance thus dissecting the intimal layer and the occlusion from the remainder of the vessel wall to a position distal of the occlusion. The ring stripper is then removed and a remote cutter, such as described in U.S. Pat. No. 5,843,102, can be used to transect the separated intimal layer distally of the occlusion. This permits the intimal layer and the occlusion to be removed through the single incision proximal of the occlusion.
One of the problems with conventional remote endarterectomy procedures occurs because removing the intimal layer and obstruction tends to pull sections of the intimal layer away from the remainder of the vessel wall at the point of transection. This leaves flaps of the transected intimal layer partially obstructing the lumen of the vessel. The intimal layer flaps interfere with the passage of a guidewire to a position distal of the transected intimal layer. Guidewires are used for many purposes, such as to guide passage of a balloon, stent or other endoluminal prosthesis into position to secure the intimal layer flaps outwardly against the remainder of the vessel wall. However, the obstruction caused by the intimal layer flaps tends to deflect the guidewire into the natural dissection plane between the tunica intima and the tunica media. Guidewire placement can occasionally be a tedious and time consuming procedure for the surgeon. If the guidewire enters this natural dissection plane, it may travel distally along the plane, giving the surgeon are impression that the true lumen has been accessed when in fact the surgeon has created a false lumen. This can also create damage to the vessel, forcing conversion to conventional bypass surgery. If it is not possible to pass the guidewire past the intimal lining flaps, the surgeon may be forced to make a separate incision past the transected intimal layer and use this second opening into the vessel to permit the guidewire to be passed retrograde through the second incision, through the vessel and out through the first incision. At times it may be required that the vessel be opened up surgically at the end point and treat the intimal lining flap surgically. Both of these latter two options largely negate the advantages of the remote endarterectomy procedure.
PCT publication WO 00/18323 discloses apparatus for guiding a guidewire between the intimal and adventitial layers of a blood vessel wall, past an occlusion and back into the main lumen distal of the occlusion. The device, however, lacks structure which would help maintain the end of the catheter body between the intimal and adventitial layers. It also lacks structure which would limit the distance the guidewire could extend through the device and into the blood vessel. In addition to lacking any recognition of the desirability of such structure, the reference fails to recognize the desirability for the use of a contrast medium to ensure the guidewire has properly accessed the distal lumen.
The present invention provides an assembly and method by which a guidewire can be positioned across a vascular occlusion prior to removal of the occlusion. This eliminates the problems associated with guidewire placement following removal of a total occlusion by a remote endarterectomy procedure. The invention is not limited to endarterectomy procedures nor is it limited to blood vessels. The invention may be used with vascular structures, including arteries and veins in various locations such as iliac, SFA, renal, coronary, SV bypass grafts and the like, as well as non-vascular tubular body structures, such as bile ducts and the esophagus. The invention may be used to cross total or partial occlusions or to cross an unoccluded position along a hollow body structure. However, for ease of discussion, the invention will usually be discussed in terms of crossing a total vascular occlusion in conjunction with a remote endarterectomy procedure.
A first aspect of the invention is directed to an assembly comprising an elongate member delivery assembly and a flexible elongate member, typically a hollow needle, comprising distal and proximal portions. The elongate member delivery assembly includes an elongate body defining an axis and a laterally-extending layer-separation guide at the distal end of the body. The guide is sized and shaped to guide the distal end of the delivery assembly between the layers of a tubular body structure. The guide helps to ensure the device stays between the chosen layers so to help prevent inadvertent puncturing or other damage to the wall. The needle delivery assembly further comprises an elongate member-redirecting surface positioned and oriented to cause the tip portion of a distally moving elongate member to be redirected to move in a direction at an angle to the axis. Thus, the tip portion of the elongate member may be directed by the assembly into the wall of a tubular body structure, along the wall between the layers of the wall, past a position (such as an obstruction) in the tubular body structure (such as a blood vessel), and back through at least one of the wall layers to enter the interior of the tubular body structure distally of the position.
The separation guide may have a width of preferably about 2-8 times, and more preferably about 4 times, as wide as the elongate body. The separation guide may have a curved cross-sectional shape. The needle delivery assembly may have a proximal end adapter at the proximal end of the body. The proximal end adapter may have a component for selecting the maximum movement of the elongate member through the lumen of the body in a distal direction. The separation guide may be moveable between a laterally retracted state and a laterally extended state to permit the assembly to be used percutaneously. The elongate body may include a hollow outer sheath, from which the separation guide extends, and an elongate member support element housed within the outer sheath and at least partly defining an elongate member pathway, the elongate member support element comprising the elongate member-redirecting surface.
A second aspect of the invention is directed to a method for crossing a position along a tubular body structure, such as a vascular occlusion, comprising selecting a position-crossing assembly comprising a flexible elongate member and an elongate member delivery assembly. The delivery assembly comprises an elongate body, a laterally-extending separation guide and an elongate member-redirecting surface positioned and oriented to cause the tip portion of a distally moving elongate member to be redirected to move in a direction at an angle to the axis of the body. The method further includes positioning the laterally-extending separation guide between layers of the wall of the tubular body structure; passing the guide between layers from a position proximal of a position within the blood vessel interior to a position distal of the position, typically past an obstruction; and then driving the elongate member along the axis in a distal direction against the deflecting surface thereby deflecting the tip portion causing the tip portion to pass through at least one wall layer and into the interior of the hollow body structure.
The method may include adjusting the maximum distance the elongate member may extend distally past the elongate member-redirecting surface. The method may also include injecting a detectable substance through the elongate member and into a blood vessel interior following the driving step to ensure the tip is properly positioned, typically within the vessel interior distal of an occlusion. The selecting step may further comprise choosing a laterally-extending, vascular tunica-separation guide having a shape which defines a curved tunicae-separation plane, the plane sized to generally follow the curvature of the blood vessel. The positioning step may be carried out percutaneously; the positioning step may comprise changing the state of the tunica-separation guide from a laterally-retracted state to a laterally-extended state to aid percutaneous placement. It should be noted that although the invention has been described in terms of use in permitting a guidewire to cross an occlusion, it could be used when a vessel is not totally occluded or in situation where the vessel is not occluded at all.
Other features and advantages of the invention will appear from the following description in which the preferred embodiments and methods are set forth in detail in conjunction with the accompanying drawings.